1. Field of the Invention
The present invention generally relates to a method for electroplating metal wire, especially for electroplating low-resistance metal wire on large-area substrate and reducing the number of photolithography masks for processing thin-film transistors (TFTs) with a structure of gate overlap lightly-doped drain (source) (GOLDD).
2. Description of the Related Art
With the advance of processing technology, the large-area TFT (Thin Film Transistor) displays will be generalized. Then some problems are going to be revealed in producing, generally the wiring on substrate is getting complicate, then the RC-delay caused by the increasing wire resistance (R) and related capacitance (C) will impact the efficiency factors of device, like the cross talk and power consuming, especially the signal transmission speed. As the featuresize of semi-conducting technology becomes smaller, it is more difficult to prevent the RC-delay, which occurs as the width of wire and distance between wires are getting smaller, then there will increase the serial resistance and the capacitance among those connecting.
Copper (Cu) and silver (Ag) have the lowest resistance among metals, which provide the simplest and directly way to reduce the connecting resistance and capacitance, but they couldn't be fabricated on glass substrate through prior photolithographing and etching technology.
Further, for fabricating the copper wire on large-area substrate, the prior art method adopts a complicate and expensive chemical mechanical polishing/planarization (CMP) process, which is a planarization technology in semi-conducting processing. The planarization is used to planarize the roughness on doping layer of semiconductor device by the cooperation of chemical etching and mechanic polishing processes.
Therefore, there needs to provide a method for electroplating metal wire to improve the RC-delay characteristics among the wires on glass substrate and the method for electroplating low-resistance metal on it. The structure of gate overlap and lightly-doping drain (source) of present invention can reduce the number of processing masks.